Method of cleansing filter cloths



U088 liclerence 1 Patented Apr. 30, 1940 METHOD OF CLEANSING FILTER CLOTHS Anton Volz, Ludwigshafen-on-the-Rhine, Germany, assignor to Hall Laboratories, Inc., Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Application February 8, 1938, Se-

5 encrustation built up on filter cloths as a result these filter cloths was generally carried out by 5 of repeated use. the use of alkaline solutions, for example, solu- Filter presses and filter bags are used in many tions of caustic soda followed by treatment in chemical processes to free liquors from undecold to hot hydrochloric acid solution. In spite sirable sediment. This invention is particularly of this treatment, however, a continually greater applicable to the treatment of filter cloths which amount of encrustation formed during use of the 10 have been encrusted with a sediment containing filter, thereby decreasing the efiiciency of the albumin and also insoluble calcium and magfilter and causing rapid wear and tear of the high nesium compounds. The term filter cloth is grade and expensive filter cloths. used in its broad sense to include not only textile It has also been proposed to use in the treatmaterials but also other filtering elements. en of filter 01013115 q e Solutions of. p 1

In the sugar industry, juice is extracted from phoric acid of any hydration sta e or aqueous sugar cane or beet, lime is added and heat is apsolutions of its alkali or ammonium salts, espeplied to precipitate the albuminoids present in cially mix f alkali metaphosphate, Py the liquor. This process separates nearly all the phosphate and P yp p Such as Sodium albuminoids and a part of the acids, fat wax, and tetraphosphate and sodium tripolyphosphate,

gums. Phosphoric acid or acid phosphate of lime with alkali orthophosphates. However, such reis often used in this purification, since it forms ag a not P d entirely Satisfactory- If a voluminous precipitate which carries down a new or a slightly encrusted filter cloth is treated much fiocculent and.,some coloring matter. The in a W Solution of Such P p it is 5 1 liquor is allowed to settle and then the clear fluid ee in keeping e fi e 0 0t Clean for a time. 95

is decanted from the sediment at the bottom of w v it is t fi t v i r m v the enthe tank. The sediment is pumped into filter crustation from thickly encrusted filter cloth. presses and th filter d jui btained h r i These filter cloths, even after undergoing a rather combined with the decanted liquor and subjected 0 8 S g in S Solutions. feel slimy but t e to further treatment. deposit is not satisfactorily removed. The treat- 30 I th manufa tur of beet, u ar, arb ni ment does not succeed in satisfactorily loosening acid is commonly added to the extracted juice the s a d us t either by p ated washduring purification, precipitating lime'as a carlngs or even by acidification with hydrochloric bonate and salts of the acids of the juice which acid, because 0 drying e filter Cloth again are removed in the filter press. feels Stiff- 35 Th preparation of b r als i v lv sep- I have found, however, that after treatment of aration of the liquor from the sediment from the the 010th in p p fi bath the encrustation rt by th use of filter bags r filter presses can be easily converted into a loosened form, if

Thus the sediment found on the filter cloths it is Placed in an aqueous diaZOtiZing Solution.

40 may contain albuminoid materials, lime comwhich may be either cold 07." warm. After treat- 40 pounds of phosphate or carbonate, as well as ment in the diazotizing solution, the filter cloth c0mp1ex organic fats a d w may be neutralized, if necessary, and then sub- It is an object of the present invention to prolected to p e s s, whereby the transforvide a method for cleansing the filter cloths used mation product f the r station is washed 5 in the presses or filter bags which are encrusted away. In this manner, there is obtained again with the sediment removed from the liquor in a soft usable filter cloth without the pulp being any of these or analogous industries. affected.

Although the invention is applicable generally This treatment may be employed to cleanse to the cleansing of filter cloths, it will be defilter cloths other than those which hav b scribed herein more particularly as applied to used in the P eparation of beer and having enrial No. 189,383. 1937 This invention relates to a method of cleansing filter cloths used to remove undesirable sediment and precipitate from fluids. It provides a method for quickly and efficiently removing the the cleansing of brewery filter cloths to remove from them the encrustation which they collect on being used. In the preparation of beer after cooking, cooling and draining of the wort, the

sediment left behind is filtered through a filter In Germany February 19,

3 Claims. (Cl-S'b-S) bag or pressed thro gh a filter press. This sediment consists of -70% albumin and also the phosphates of calcium and magnesium, besides cellulose, hop resin, etc. Heretofore washing crustations of albuminous and alkaline-earth deposits which make the usual processes of cleansing the filter cloths impractical. The following are specific examples of various ways in which the present invention may be carried out, it being understood that these are given by way of example only, and not by way of limiting the inven tion thereto.

Example 1 The wet filter cloth coming from the press is freed from the adhering sediment first by mechanical treatment and then, either wet or after drying, is soaked at a temperature of about -40 C. in a solution containing one gram of sodium tetra-phosphate (NasP4O1s) and one gram of disodium phosphate per liter. It is then rinsed and put in a warm bath of about 10 C. containing three grams of sodium nitrite and nine cubic centimeters of hydrochloric acid of 20 Baum per liter. After treating in this bath for about one-half hour, it is removed and rinsed further with fresh water. This produces a soft usable filter cloth from which the encrustation has been substantially completely removed.

Example 2 The filter cloth coming from the press is soaked at a temperature of about C. in an aqueous solution containing two grams of sodium metaphosphate and one gram of sodium carbonate per liter. It is then rinsed and treated in a diazotizing solution, as given in Example 1.

Example 3 The filter cloth is first treated with an aqueous solution containing one gram of ammonium and one gram of tetrasodium pyrophosphate per liter and is then put into a diazotizing solution bath, as in Example 1.

Example 4 The filter cloth coming from the filter press is rinsed in luke warm water and soaked in a warm solution (40 C.) containing one gram of sodium pyrophosphorio acid and one gram of sodium hexametaphosphate per liter. It is then rinsed and treated as indicated in Example 1, with a diazotizing solution.

The phosphate bath which precedes the diazotizing bath may contain phosphoric acid in any hydration stage, or it may contain the alkali or ammonium salts of phosphoric acid. The term phosphate solution as used in the claims is intended to cover broadly any solution of a phosphate, whether that be orthophosphate, metaphosphate, pyrophosphate, polyphosphate or mixtures of any of them. It also is intended to include the corresponding phosphoric acid or mixtures of the corresponding phosphoric acids.

The term molecularly dehydrated phosphates is intended to include the metaphosphates, pyrophosphates and polyphosphates, or the corresponding phosphoric acids, since they may be considered as derived from orthophosphoric acid or the salts thereof by dehydration which efiects an atomic rearrangement within the phosphate molecule.

Although I have given certain examples of the manner in which the invention may be practiced, it is to be understood that the invention is not limited thereto but may be otherwise embodied or practiced within the scope of the following claims.

I claim: v

1. The method of cleansing filter cloths soiled with albuminous and alkaline earth deposits, which comprises soaking them in an aqueous solution of a molecularly dehydrated phosphate and thereafter in an aqueous nitrous acid solution.

2. The method of cleansing filter cloths soiled with albuminous and alkaline earth deposits, which comprises soaking them in an aqueous solution of a mixture of an alkali-metal molecularly dehydrated phosphate and an alkali-metal orthophosphate, and thereafter in an aqueous nitrous acid solution.

3. The method of cleansing filter cloths soiled with albuminous and alkaline earth deposits;

which comprises soaking them in an aqueous metaphosphate solution and thereafter in an aqueous nitrous acid solution.

- ANTON VOLZ. 

